Thermal switch



April 23, 1940. G. H. LELAND THERMAL SWITCH Filed June 10. 1937 3 Sheets-Sheet 1 A T TUENE I I I u I I H V April 23, 1940. LELAND 2,198,502

THERMAL SWITCH Filed Jun 10, 19:57 a Sheets-Sheet '2 /NVEN TUE. EEDFE'EH. LELAND.

M; A T TUENEY.

April 23, 1940. s. H. LELAND THERMAL SWITCH Filed June 10, 1937 3 Sheets-Sheet 5 /N\ EN7'L7F GEUFE'E H. LELAND.

A TTUFrA/E Y.

Patented Apr. 23, 1940 PATENT OFFICE THERMAL SWITCH George H. Leland, Dayton, Ohio, assignor to The Leland Electric Company, Dayton, Ohio, a. corporation of Ohio Application June 10, 1937, Serial No. 147,531

24 Claims.

This invention relates to a thermal switch and is designed primarily as a protecting device for electrical apparatus such as an electric motor.

One object of the invention' is to provide a thermal switch which will be simple in construction and positive in its operation and which can be produced at a low cost.

A further object of the invention is to provide a thermostat which will operate such a switch 16) with a snap action to quickly open and close the circuit.

A further object of the invention is to provide such a thermostat which can be easily adjusted to vary the temperatures at which the switch will 16 open and close.

A. further object of the invention is to provide such a switch with manually operated means for controlling the closing of the circuit.

A further object of the invention is to provide 20 sucha switch with manually operable controlling means of such a character that the switch cannot be closed thereby until the heat responsive element has cooled to a predetermined temperature.

A further object of the invention is to provide 25 such a switch which may be easily converted from the manually controlled type to the selfclosing type.

A further object of the invention is to provide a thermal switch which will control two cir- 30 cuits and which will open and close said circuits either separately or simultaneously.

Other objects of the invention may appear as the apparatus is described in detail.

In the accompanying drawings Fig. 1 is an 35 edge view of a thermal switch embodying my invention; Fig. 2 is a front elevation of such a switch; Fig. 3 is an end view of said switch showing the same in circuit closing position; Fig. 4 is a similar view showing the switch in circuit 40 opening position; Fig. 5 is an edge view of the switch showing the same provided with a heating element; Fig. 6 is a front elevation of the switch shown in Fig. 5; Fig. '1 is a front elevation of a switch showing the same provided with a 45 manually controlled latch for retaining the same in circuit opening position; Fig. 8 is a plan view of the controlling member in its circuit opening position; Figs. 9, 10, 11 and 12, are detail views showing the latch and heat responsive member 50 in different relative positions; Fig. 13 is an edge view of a two circuit switch; Fig. 14 is a front elevation of the two circuit switch; Fig. 15 is a detail view of the controlling element; Figs. 16, 1'7 and 18, are detail views showing differ- 55 cut relative positions of the controlling element and heat responsive members of the two circuit switch; Fig. 19 is an edge view of a switch having a non-resilient controlling member; Fig. 20 is a front elevation of the switch of Fig. 19; Fig. 21

is a sectional detail view of the non-resilient con- 5 trolling member; and Fig. 22 is a sectional view of the end frame of an electric motor showing the switch mounted therein.

In these drawings I have illustrated several embodiments of the invention, each of which comprises two members arranged in substantially parallel planes and having at adjacent ends parts spaced one from the other in a direction substantially parallel with the planes of said members, the arrangement being such that when the device is in a vertical position, as shown in the drawings, and is in circuit closing position, the end portions of the members will lie in different vertical planes and will be spaced vertically one from the other. At least one of these members is heat responsive and is provided with a contact which cooperates with a normally stationary contact. Interposed between the end portions of the two members is a controlling member, preferably in the form of a compression spring, which, when 25 the switch is in circuit closing position, extends at an acute angle to the planes of the two members and thus tends to hold the heat responsive element in circuit closing position and to resist its initial movement from that position. When the heat responsive member is subjected to a predetermined temperature it will acquire a force suflicient to overcome the resistance of the controlling element and will move toward the circuit opening position, thus moving the controlling element into a substantially vertical position, that is,'substantially parallel with the planes of the two members, in which position the controlling element will resist the movement of the heat responsive member in circuit closing direction 40 until the temperature has fallen to a predetermined extent, at which time the heat responsive member will overcome the resistance of the controlling element and move quickly to its circuit closing position. As the controlling element moves from one position to the other the resistance offered thereby to the heat responsive member rapidly decreases thus permitting that element to move quickly from one position to the other with what is in effect a snap action. 60

In Figs. 1 to 4 the switch comprises a thermostat in the form of a bimetallic bar which is bent upon itself to form the two members, 25 and 26, which are of substantially equal length and arranged in substantially parallel planes spaced laterally one from the other. Preferably the bars are so bent that they diverge edgewise toward their outer ends. As shown in the drawings these members are arranged edgewise in substantially vertical planes but it will be understood that the switch may be mounted in any desired position. The member 26 is rigidly secured near its outer end to a U-shaped bracket 21, as by means of a rivet 28, the end portion of the member 26 extending beyond the bracket 21. This bracket is rigidly secured to and insulated from a supporting structure, such as a base plate 29, which may, if desired, be of insulating material. The member 25 is movable toward and from the plane of the member 26 and carries a contact member 30 which cooperates with a normally stationary contact 3| carried by the base plate 29. This normally stationary contact is preferably adjustable and is here shown as carried by a resilient conductor bar 32 which is rigidly secured at one end to the base plate and to a terminal 33 to which one side of the circuit is attached. The bracket 21 forms-a part of the circuit and one arm thereof extends through the base plate and is provided on the rear side of that plate with a terminal 34, so that when the switch is in its closed position the current flows from the terminal 33 to the stationary contact, through the two members of the bimetallic bar, and through the bracket 21 to the terminal 34 which is connected with the other side of the circuit. Mounted in the base plate is a screw 35 which engages the resilient bar 32, which carries the stationary contact, and serves to adjust that contact with relation to the base plate, so as to vary the temperature to which the bimetallic bar must be subjected in order to open the circuit. It will be understood of course that the bimetallic bar is of such construction that when subjected to excessive temperature it will flex in such a direction as to move the member 25 thereof in circuit opening direction.

For the purpose of retaining the movable contact 30 in either its circuit closing or circuit opening position until there has been a predetermined change in temperature and then moving the same quickly from one position to the other I have interposed between the two members 25 and 26 a controlling member which is preferably in the form of a compression spring. To this end the member 25 is provided with a part 36 which projects beyond the bracket 21 and the member 26 is provided with a part 31 which projects beyond that bracket. These parts of the two members are spaced one from the other edgewise of the members 25 and 26 so that when the switch is in circuit closing position, as shown in Fig. 3, the two parts will lie in spaced vertical planes and will be spaced vertically one from the other. The controlling member is preferably in the form of a coiled spring 38 having at its ends socket members 39 to receive knife edge pivots on the members 25 and 26 respectively. Thus with the parts in circuit closing position the controlling spring will extend at an acute angle to the planes of the members 25 and 26 and will hold the movable contact 30 in engagement with the stationary contact 3| and resist its movement in circuit opening direction until the bimetallic bar has accumulated suflicient force to overcome the resistance of the spring. As soon as sufficient force has been accumulated in the movable member the latter will move in circuit opening direction and will move the controlling spring toward a position substantially parallel with the planes of the members 25 and 26, as shown in Fig. 4, the movement of the member 25 in circuit opening direction being limited by its contact with the bracket 21. As the spring moves toward its parallel or vertical position its resistance to the movement of the member 25 rapidly decreases, thus permitting that member to move very quick ly from circuit closing position to circuit opening position, and when the member 25 is in circuit opening position the controlling spring, which is then in or slightly beyond a position parallel with the planes of the members 25 and 26, will resist the initial movement of the member 25 in circuit closing direction. When the temperature has fallen to a predetermined extent the pressure of the member 25 will overcome the resistance of the spring and move to circuit closing position, thus moving the spring to its initial inclined position and as this movement progresses the resistance of the spring to the movement of the member 25 decreases and its expansion tends to expedite that movement, so that the circuit will be quickly closed. The spring 36 connects the two ends of. the bimetallic bar but it comprises a relatively great length of high resistance wire and the amount of current which can pass through the same is negligible and does not appreciably aiTect the action of the thermostat.

In the preferred construction a U-shaped clip or reinforcing member 40, preferably also bimetallic, is mounted about the bent portion of the thermostatic bar and one arm of this clip is riveted or otherwise rigidly secured to the member 25, as shown at 4|, and the other arm carries an adjusting element which acts upon the member 26 so as to regulate the flexing thereof and vary the 'low temperature at which the member 25 will move from circuit opening to circuit closing position. As here shown, this adjusting element is in the form of a screw 42 mounted in the clip 40 and swiveled in or otherwise connected with the member 26 for rotation with relation thereto, as shown at 43. The arm of the clip 40 is slotted and the edges of the slot are turned up, as shown at 44, to engage the threads of the screw 42 and form a screw threaded connection therewith and at the same time to permit the slotted arm and the member 26 to have a slight relative movement lengthwise thereof.

It is not essential that the bimetallic bar should be bent upon itself to form two members, as shown, but, if desired, a straight or substantially straight bar could be used and in this event the part 31 which is connected with one end of the controlling spring would be separate from the bimetallic bar and the device would operate in the same manner. However, by bending the bar to the-shape shown the benefit of the long bar is secured in a thermostat of relatively short length.

In some installations it may be desirable to provide additional means for heating the heat responsive member and in Figs. 5 and 6 I have shown a switch similar to that shown in Figs. 1 to 4, which is provided with a heating element. As there shown, a heating element 45, which may be of any suitable character, is connected at one end with the bracket 21, as shown at 46, and is connected at its other end with a terminal 41 with which one side of the circuit is connected, this terminal 41 being substituted for the terminal 34 above mentioned.

The switch above described is of the self-closing type and is wholly automatic in its operation, that is, it automatically opens at a predetermined high temperature and automatically closes at a predetermined lower temperature. However, in some installations it is desirable that the closing should be manually controlled and to this end it 'is necessary to provide means to retain the movable contact in circuit opening position until it is manually released. In Figs. 7 to 12 I have shown a switch, similar to that shown in Figs. 1 to 4, which is provided with means controlled by the opening movement of the movable member 25 for latching the same in its open position and retaining the same in that position until the latch is manually operated to release the same. Preferably the latch is of the construction shown at 58 and is pivotally mounted between its ends on a pivot pin 49 carried by a small bracket 50 rigidly secured to the main bracket 21. This latch has a flange 5i extending inwardly across one side of the bracket 21, that portion of the flange on one side of the pivotal axis 49 of the latch being arranged in the path of the opening movement of the member 25. On the other side of the pivotal axis the latch is provided with a part extending inwardly beyond the flange 5| and having an upturned finger 52 adapted to be moved into and out of the path of the closing movement of the member 25. When the switch is in circuit closing position, as shown in Fig. 9, the bracket will be in the position there shown, with the finger 52 in an inoperative position with relation to the member 25. As the member 25 completes its circuit opening movement it will engage the flange 5| and rock the latch about its axis to move the finger 52 into the path of the member 25, the latter entering the recess formed between the finger and the flange 5|, as shown in Fig. 10. When the temperature has dropped sufficiently to permit the member 25 to move toward circuit closing position the latter will engage the finger 52 which will interrupt its movement before the contact 30 has engaged the stationary contact 3|, as shown in Fig. 12, thus preventing the closing of the circuit until the latch is operated to release the member 25. The latch may be manually operated in any suitable manner, as by means of a plunger 53, slidably mounted in the wall of a casing enclosing the switch and arranged to engage the latch and tilt the same to releasing position. When the latch is so tilted the member 25 is released and permitted to complete its closing movement. It is desirable that the controlling means should be of such a character that the circuit cannot be closed before the temperature has fallen to the desired extent and the present latch is of such a character that it cannot be operated to close the switch but merely to release the member 25 and permit the latter to close the circuit by its own action. That portion of the flange 5| of the latch, which engages the member 25, is of such a width that when the latch is moved to releasing position the outer part thereof will engage the bracket 21 and interrupt the movement of the latch before the member 25 has been moved to circuit closing position, as shown in Fig. 11. Thus it is impossible for the operator to immediately restart a motor by manually closing the switch after it has been automatically opened. If he presses the plunger 53 inwardly and then releases the same, before the thermostat has cooled, the member 25 will immediately restore the latch to the position shown in Fig. 10. If he continuesto press the plunger inwardly the member 25 will merely be held in the intermediate position shown in Fig. 11 until it has cooled sufllciently to close by its own action.

This switch when provided with the latch can be quickly and easily converted from a manually controlled to a self-closing switch by merely providing means for retaining the latch in its inoperative position, as shown in Fig. 9. This may be accomplished in various ways and in Fig. 9 I have shown a spring 55 mounted onthe casing which encloses the switch for movement into and out of engagement with the outer end of the plunger 53. When this spring is in engagement with the plunger, as shown, the latch will be retained in its inoperative position and the switch will operate as a self-closing switch. When the spring is moved out of engagement with the plunger the latch will operate as above described and the switch will be a manually closing trip free switch. When the latch is locked in its inoperative position the member 25 will have less opening movement than it will have when the latch is operative, the limit of this movement being shown in Fig. 11. in order that the controlling member may retain the member 25 in either of its open positions that part of the member 25 which engages the end of the controlling element is offset inwardly, as shown at 55 in Fig. 8, so that when the member 25 is moved to the position shown in Fig. 11 the controlling spring will be in a substantially vertical position and will resist the initial closing movement of the member 25. When the member 25 is moved to its fully open position, as shown in Fig. 10, the controlling spring will be tilted beyond its vertical position, as shown in Fig. 8, and will also function to resist the initial closing movement of the member 25.

In Figs. 13 to 18 there is shown a switch of this type adapted to control two circuits and to open either of said circuits individually or to open both circuits at the same time. In the particular construction illustrated this two circuit switch comprises a supporting structure consisting of two base plates 58 spaced apart and rigidly connected one to the other. These base plates carry on their inner sides stationary contacts 59 and 60 which are adapted to be connected with one side of the respective circuits. Arranged between the base plates are two heat responsive elements, such as bimetallic bars 5| and 52, which are arranged in parallel planes and are secured at one end to the respective base plates and at their other ends are provided with contact members '63 and 34,- respectively, adapted to cooperate with the respective contacts 59 and 60. The heat responsive elements or bimetallic bars may be of any suitable character, such for example as that previously described, but as illustrated they are in the form of substantially straight bars and are connected with terminals at their points of connection with the base plates. At its free end each bar is provided with a part having a knife edge, as shown at 53 and 54, these parts being spaced one from the other edgewise of the bimetallic bars. Interposed between these parts 63 and 54 is a controlling element, here shown as a compressed spring 55 similar to that above described with the exception that an insulating washer 6B is interposed between the spring and each of the caps 61 with which the pivot members 63 and 84 engage. When both movable contacts 63 and 64 are in circuit closing position the controlling spring 55 will be inclined, as shown in Fig. 11, so as to exert outward pressure on both the members 8| and 52 and thus resist their initial movement 75 from their circuit closing positions. It the two heat responsive members are subjected to substantially the same temperatures so that they will flex substantially uniformly both movable contacts will be moved to circuit opening positions at substantially the same time and the controlling spring will be moved from the position shown in Fig. 16 to that shown in Fig. 17 in which it is inclined slightly in a direction opposite that shown in Fig. 16 and will thus tend to resist the initial movement of both movable contacts toward circuit closing positions. Preferably the bimetallic members are provided with stops 68 which engage the respective base plates 58 and limit the movement of the members in circuit opening directions. If one bimetallic member should receive excessive heat while the temperature of the other member remains substantially normal the excessively heated member would move to circuit opening position, as shown in Fig. 18, and thus move the controlling spring into a position substantially parallel with the planes of the two bimetallic members, in which position it would resist the movement of that member which is in circuit opening position toward circuit closing position. In either event when the temperature of the member or members which are in circuit opening positions falls below the predetermined temperature they will be moved to circuit closing position and the controlling member restored to its initial inclined position.

While I prefer to use a compression spring as the controlling element this is not essential to the operation of the device and the controlling element may take various forms. In Figs. 19 to 21 I have shown the same as a block of insulating material 10- provided at its ends with recessed metal plates 1| to form pivot seats, adapted to receive pivot points 12 on the two members 13 and 14 of the switch. The pivots are in this case points rather than knife edges so as to permit a relative movement about the longitudinal axis 01' the controlling element as well as about transverse axes. The members 73 and 14 comprise parts of a bent bimetallic bar, such as above described, and difier from the construction shown in Figs. 1 to 4 only in that the bend of the bar is on a longer radius, as shown at 15. This permits the movable member to have a slight yielding movement as the controlling element moves from its inclined to its vertical position and thus provides the necessary resilience to retain the controlling member in its adjusted positions.

When the switch is used for the purpose of protecting an electric motgit is usually mounted within the motor frame and may be arranged in any desired position in that frame. However, I have found that the thermostat will have a more desirable behavior if it is protected against the air which circulates through the motor casing and, as shown in Fig. 22, I have provided the end frame of the motor casing with a cavity 16 in which the switch is mounted, the base plate 29 serving to close or to substantially close the inner side of the cavity so that little or no air will enter the cavity. Thus the thermostat is subjected to the temperature generated in the circuits, unaffected by other conditions, and will respond accurately to current conditions.

While I have shown and described certain embodiments of my invention I wish it to be understood that I .do not desire to be limited to the details thereof as various modifications may ocour to a person skilled in the art.

Having now fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A thermostat comprising two bimetallic strips arranged, edgewise in substantially parallel planes and having one pair of opposed ends held against relative movement and having the other pair of opposed ends relatively movable in substantially parallel planes at substantially right angles to the first mentioned planes, said strips having opposed knife edge pivots adjacent the movable ends of the respective strips, extending lengthwise thereof and spaced apart in a direction transverse to said strips and substantially parallel with the first mentioned planes, and a compression spring engaging said pivots and arranged to act on said strips both in a direction substantially parallel with said first mentioned planes and in a direction transverse to said first mentioned planes.

2. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and having opposed parts spaced one from the other in a direction transverse to said members and substantially parallel with said planes, said part of one of said members being held against movement and the other of said members being heat responsive to move its said part transversely to the plane of the first mentioned part, and a controlling member extending between said transversely spaced parts of said members in a substantially straight line approximately parallel with said planes, said controlling member being pivotally connected at its opposite ends with said parts and so arranged that it will yieldably resist the initial movement of said heat responsive member and said resist ance will decrease as said part of said heat responsive member moves toward the plane of the other of said parts.

3. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and provided at adjacent ends with parts spaced one from the other in a direction transverse to said members and substantially parallel with said planes, at least one of said members being heat responsive to move its said part transversely to the plane of the other member, and a controlling element confined between and pivotally connected with said transversely spaced parts of said members for movement with relation thereto about axes extending lengthwise of the respective members.

4. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and provided at adjacent ends with parts having opposed pivot edges spaced one from the other in a direction transverse to said members and substantially parallel with said planes, at least one of said members being heat responsive to move its said part transversely to the plane of the other member, and a controlling element having engagement at its opposite ends with the respective pivot edges of said members and movable thereon about axes extending lengthwise of the respective members.

5. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and provided at adjacent ends with parts spaced one from the other in a direction transverse to said members and substantially parallel with said planes, at least one of said members being heat responsive to moveits said part transversely to the plane of the other member, and a yieldable controlling element confined between and pivotally connected with said trans- 76 versely spaced parts for movement with relation thereto about axes extending lengthwise of the respective members.

'6. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and provided at adjacent ends with parts spaced one from the other in a direction transverse to said members and substantially parallel with said planes, said part of one of said members being fixed against .movement and the other of said members being heat responsive to move its said part transversely to the plane of the first mentioned member, and a longitudinally yieldable element interposed between and pivotally connected with said parts of said members for movement about axes extending lengthwise of the respective members, said element extending normally at an acute angle to the planes of said members and being movable by said heat responsive member to or beyond a position substantially parallel with said planes.

7. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and provided at adjacent ends with parts spaced one from the other in a direction transverse to said members and substantially parallel with said planes, at least one of said members being heat responsive to move its said part transversely to the plane of the other member, and a coiled spring interposed between and pivotally connected with said parts for movement about axes extending lengthwise of said members, said spring extending normally at an acute angle to the planes of said members and being movable by said heat responsive member to or beyond a position substantially parallel with said planes.

8. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and provided at adjacent ends with parts spaced one from the other in a direction transverse to said members and substantially parallel with said planes, at least one of said members being heat responsive to move its said part transversely to the plane of the other member, and a controlling element interposed between and pivotally connected with said parts of said members for movement about axes extending lengthwise of the respective members, said controlling element extending normally at an acute angle to the planes of said members to yieldably resist the movement of said heat responsive member from its normal position and being movable by said heat responsive member when the latter has acquired a predetermined force to a position in which it will resist the initial movement of said heat responsive member toward its normal position.

9. A thermostat comprising two elongate members arranged in substantially parallel laterally spaced planes and provided at adjacent ends with opposed knife edge pivots extending lengthwise thereof and spaced one from the other in a direction transverse to said members and substantially parallel with said planes, at least one of said members being heat responsive to move the end portion thereof transverse to the plane of the other member, and a substantially straight controlling member supported by said members with its opposite ends in pivotal engagement with the respective knife edge pivots.

10. A thermostat comprising a bimetallic bar bent upon itself to form two'members spaced laterally one from the other, the ends of said bar having parts spaced one from the other edgewise of said bar, one of said members being secured adjacent its said part to a fixed support and the other of said members being movable to move said part thereof toward and from the plane of the first mentioned part, and a controlling element interposed between and pivotally connected with said parts for movement about axes extending lengthwise of the respective members and arranged to yieldably resist the initial movement of said movable member and to be moved by said movable member to or beyond a position substantially parallel with the planes of said members.

11. A thermostat comprising a bimetallic bar bent upon itself to form two members spaced laterally one from the other and diverging edgewise toward their outer ends, the outer end portions of said members being spaced one from the other edgewise thereof, the outer end portion of one of said members being mounted on a fixed support and the outer end portion of the other member being movable toward and from the plane of the end portion of the first mentioned member, and a compression spring interposed between the spaced end portions of said members and arranged to hold said movable end portion in its initial position until said thermostat is subjected to a predetermined temperature and to be then moved by said movable end portion to a position in which it will resist the movement of said movable end portion toward its initial position until said temperature falls to a predetermined extent.

12. A thermostat comprising a bimetallic bar bent upon itself to form two members spaced laterally one from the other, the ends of said bar having parts spaced one from the other edgewise of said bar, one of said members being secured to a fixed support and the other of said members being movable to move said part thereof toward and from theplane of the other of said parts, a controlling element interposed between said parts and arranged to yieldably resist the initial movement of said movable member and to be moved by said movable member to or beyond a position substantially parallel with the planes of said members, a substantially U-shaped m mber mounted about the bent portion of said bar and secured to one member thereof, and an adjustable part carried by said U-shaped member and engaging the other member of said bar.

13. A thermostat comprising a bimetallic bar bent upon itself to form two members spaced laterally one from the other, the ends of said bar having parts spaced one from the other edgewise of said bar, one of said members being secured to a fixed support and the other of said members being movable to move said part thereof toward and from the plane of the other of said parts, a controlling element interposed between said parts and arranged to yieldably resist the initial movement of said movable member and to be moved by said movable member to or beyond a position substantially parallel with the planes of said members, a substantially U-shaped member mounted about the bent portion of said bar and having one arm thereof rigidly secured to the movable member of said bar, and an adjusting device mounted on the other arm of said U- shaped member and connected with the other member of said bar.

14. A thermostat comprising two bimetallic members spaced laterally one from the other and one of said parts being movable by the member of which it is a part into substantial alinement with the other of said parts, a normally inclined controlling element interposed between and pivotally connected with said parts lengthwise of the respective members to yieldably resist the initial movement of said part from its normal position until said thermostat is subjected to a predetermined temperature and to then release said movable part for movement, and a retaining device movable by said movable part to a position to prevent the return movement of said movable part and manually operable to release said movable part for said return movement;

15. In a circuit controlling device, a normally stationary contact, a thermostat comprising two members arranged in laterally spaced planes and having parts spaced one from the other in a direction substantially parallel with said planes, at least one of said members being heat responsive to move its said part from its normal position toward the plane of the other of said parts and being biased toward said normal position, a contact carried by said heat responsive member and cooperating with said stationary contact, a controlling element interposed between said spaced parts and arranged to yieldably retain said movable member in circuit closing position until said heat responsive member is subjected to a predetermined temperature and to then release the same for movement to circuit opening position, a retaining device having means controlled by said thermostat for moving the same into a position to retain said heat responsive member in circuit opening position and having manually operable means for releasing said heat responsive member for movement to circuit closing position.

16. In a circuit controlling device, a normally stationary contact, a thermostat comprising two members arranged in laterally spaced planes and having parts spaced one from the other in a direction substantially parallel with said planes, at least one of said members being heat responsive to move its said part from its normal position toward the plane of the other of said parts and being biased toward said normal position, a contact carried by said heat responsive member and cooperating with said stationary contact, a controlling element interposed between said spaced parts and arranged to yieldably retain said movable member in circuit closing position until said heat responsive member is subjected to a predetermined temperature and to then release the same for movement to circuit opening position, a retaining device having means controlled by said thermostat for moving the same into a position to retain said heat responsive member in circuit opening positions and having manually operable means for releasing said heat responsive member for movement to circuit closing position, said manually operable means being incapable of moving said heat responsive member to circuit closing position.

1'7. In a circuit controlling device, a normally stationary contact and a movable contact, a heat responsive member for moving said movable contact into and out of circuit closing position, and a latch supported independently of and movable by said heat responsive member to a position to retain said member in circuit opening position and having manually operable means for moving the same to a position to release said member.

18. In a circuit controlling device, a normally stationary contact and a movable contact, a heat responsive member for moving said movable contact into and out 01'. circuit closing position, and a latch movable by said heat responsive member to a. position to retain said member in circuit opening position and having manually operable means for moving the same to a position to release said member, said latch also having means to interrupt its movement in circuit closing direction before said member has been moved to its circuit closing position.

19. In a circuit controlling device, a normally stationary contact and a movable contact, a heat responsive member for moving said movable contact into and out of circuit closing position, and a pivoted latch having on one side of its pivotal axis a part movable into and out of a position to retain said member in circuit opening position and having on the other side of its pivotal axis a part arranged to be actuated by said member as the latter moves in circuit opening direction and to move said first mentioned part into retaining position, said latch also having a manually operable part to move said first mentioned 'part into a position to release said member.

20. In a circuit controlling device, a normally stationary contact and a movable contact, a heat responsive member for moving said movable contact into and out of circuit closing position, a pivoted latch having on one side of its pivotal axis a part movable into and out of a position to retain, said member in circuit opening position and. having on the other side of its pivotal axis a part arranged to be actuated by said member as the latter moves in circuit opening direction and to move said first mentioned part into retaining position, said latch also having a manually operable part to move said first mentioned part into a position to release said member, and means for so limiting the movement of said latch by said manually operable part that said latch cannot move said member to circuit closing position. v

21. In a circuit controlling device, a normally stationary contact and a movable contact, a heat responsive member for moving said movable contact into and out of circuit closing position, a latch movable by said heat responsive member to a position to retain said member in circuit opening position and having manually operable means for moving the same to a position to release said member, and means for retaining said latch in inoperative position, whereby the closing of the circuit will be controlled wholly by the heat responsive member.

22. In a circuit controlling device, two normally stationary contacts connected in separate circuits, two movable contacts cooperating with the respective stationary contacts, two heat responsive members arranged in substantially parallel planes and connected with the respective movable contacts, said members having parts spaced one from the other in a direction substantially parallel with the planes of said members, and a con-- trolling element interposed between said parts and arranged to yieldably resist the movement of both members from their circuit closing positions.

23. In a circuit controlling device, two normally stationary contacts connected in separate circuits, two movable contacts cooperating with the respective stationary contacts, two heat responsive members. arranged in substantially parallel planes and connected with the respective movable contacts, said members having parts spaced one from the other in a direction substantially parallel with the planes of said members, and a spring interposed between and connected with said parts and extending normally at an acute angle to the planes of said members to retain the latter in circuit closing positions against the initial action of said members.

24. In a circuit controlling device, two normally stationary contacts connected in separate circuits, two movable contacts cooperating with the respective stationary contacts, two bimetallic members having parts arranged in laterally 10 spaced and substantially parallel planes and spaced apart edgewise of said members, and a coiled spring interposed between and pivotally connected with said parts and extending normally at an acute angle to the planes of said parts to resist the initial movement of the latter in circuit opening direction, said spring being movable by the opening movement of either of said members to or beyond a position substantially parallel with said planes.

GEORGE H. LELAND. 

